<template>
  <div class="child">
    <h3>我是Child组件</h3>
    {{sum}}
  </div>
</template>

<script>
import {ref} from 'vue'
export default {
  name: 'Child',
  async setup(){
    let sum = ref(0)
    let p = new Promise((resolve,reject)=>{
      setTimeout(()=>{
         resolve({sum})
      },3000)
    })
    return await p
  }
}
</script>

<style>
.child {
  background-color: skyblue;
  padding: 10px;
}
</style>